The former chief secretary to the Treasury, Liam Byrne, has reignited criticism of Labour's stewardship of the economy with a note for his successor which said "there's no money left".

Byrne's note was discovered by David Laws, the Liberal Democrat MP who was appointed by the coalition government to succeed Byrne as No 2 at the Treasury.

It is a convention for outgoing ministers to leave a note for their successors with advice on how to settle into the job. But Byrne's note – which he later said was intended as a private joke – drew attention to Labour's economic record when it was revealed by Laws at a press conference today.

Laws told reporters: "When I arrived at my desk on the very first day as chief secretary, I found a letter from the previous chief secretary to give me some advice, I assumed, on how I conduct myself over the months ahead.

"Unfortunately, when I opened it, it was a one-sentence letter which simply said: 'Dear chief secretary, I'm afraid to tell you there's no money left,' which was honest but slightly less helpful advice than I had been expecting."

The letter recalls a similar note left by Tory Reginald Maudling to his Labour successor James Callaghan in 1964: "Good luck, old cock ... Sorry to leave it in such a mess."

Byrne said the message was meant in jest. "My letter was a joke, from one chief secretary to another," he said. "I do hope David Laws's sense of humour wasn't another casualty of the coalition deal."

Treasury sources said the full text of the letter from Byrne – dated 6 April, the day Gordon Brown called the general election – was: "Dear chief secretary, I'm afraid there is no money. Kind regards – and good luck! Liam."

Byrne's notes have caused bemusement before. When he was promoted to the cabinet in 2008, he gave officials a set of instructions entitled Working with Liam Byrne, which included the lines: "Coffee/Lunch. I'm addicted to coffee. I like a cappuccino when I come in, an espresso at 3pm and soup at 12.30-1pm ... If I see things that are not of acceptable quality, I will blame you."